Final answer:
To measure cell cycle progress via DNA content, scientists use a technique called flow cytometry. This technique involves staining cells with a fluorescent dye that binds to DNA and passing them through a flow cytometer to measure fluorescence intensity. By comparing DNA content between samples at different times, scientists can determine the phase of the cell cycle.
Step-by-step explanation:
To measure cell cycle progress via DNA content, scientists use a technique called flow cytometry. In this technique, cells are stained with a fluorescent dye that binds specifically to DNA. The cells are then passed through a flow cytometer, which measures the amount of fluorescence emitted by each cell. This fluorescence intensity is directly proportional to the DNA content, allowing scientists to determine which phase of the cell cycle the cells are in.
For example, in Sample B, if the DNA content has doubled compared to Sample A, it indicates that the cells have entered the S-phase, where DNA replication occurs. This is because during the S-phase, DNA content doubles as new DNA is synthesized. Therefore, the correct answer is b. The DNA content of the cell has doubled.